Synthesis and characterization of trivalent cations (Fe2O3, Al2O3, and B2O3) incorporated into Ca2SiO4 bioceramics: bioactivity, optical, and antibacterial properties.

Herein, divalent cations such as Ca2+, Sr2+, and Mg2+ are widely studied for their contribution to the bioactivity and performance enhancement of biomaterials intended for bone applications. The incorporation of functional ions into these bioceramics thus represents a promising and economically viable approach. In contrast, Fe, Al, and B cations, although recognized for their influence on structure, chemical stability, and certain physicochemical properties, remain relatively unexplored in relation to the bioactivity of bone-related biomaterials. The present study focuses on the development of three bioactive bioceramics, successfully synthesized by the conventional solid-state reaction method, followed by heat treatments between 100 °C and 1000 °C. These bioceramics are based on the dicalcium silicate phase (Ca2SiO4), into which bioactive trivalent cations, such as Boron oxide (B2O3), Alumina (Al2O3) and Hematite (Fe2O3) have been incorporated, named CSF, CSA, CSB respectively. Furthermore, the bioactivity of these bioceramics were evaluated by immersing them in simulated body fluid (SBF) and artificial saliva (AS) for 24 hours at 37 °C. The samples were then characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and UV spectroscopy. These analyses were complemented by using transmission electron microscopy (TEM). X-ray diffraction (XRD) results confirmed that the Dicalcium silicate (Ca2SiO4) phase is predominant in the three bioceramics, with secondary bioactive phases such as Grossite (CaAl4O7), Tricalcium borate (Ca3B2O6) and Brownmillerite (Ca2Fe2O5), specific to each incorporated oxide. The optical band gap of the samples, determined by UV-visible spectrophotometry, ranged from 3.60, 3.21 and 2.99 eV for CSF, CSB, CSA respectively. Antibacterial activity, evaluated against Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria, revealed significant inhibition of Staphylococcus aureus. XRD analyses after only 24 hours immersion in simulated media, complemented by scanning electron microscopy (SEM) observations, showed that these bioceramics rapidly promote the formation of a bone-like hydroxyapatite (Ca10(PO4)6(OH)2) layer, demonstrating their potential as biomaterials for bone regeneration. The results obtained indicate that the incorporation of bioactive oxides into dicalcium silicate may significantly improve its properties, thus enhancing its potential for tissue regeneration applications.